Safeguards against Disease 143 



use so cleverly for the welfare of the whole 

 community, they have acquired, as we have 

 said, through long ages of adaptation to new 

 conditions. By adaptation we mean making 

 the best of it. Now this power -of. adaptation 

 the body cells possess to-day, subject to the 

 work and strain of ordinary life. The body 

 cells can adapt themselves to new kinds of 

 food and to more or less of it, to changes of 

 temperature, to new forms of work, and so on. 

 Life is, in fact, a constant adjustment to 

 varying conditions. If these new conditions 

 become too extreme, the efforts of adaptation 

 are exaggerated, the capacity is overstrained, 

 the rhythm of correlated activities is broken, 

 and this is disease. But the pull of the 

 ancestral experiences, which we call heredity, 

 is ever back to the balanced activities called 

 health. This pull of the ancestral experiences 

 is what the doctors have in mind when they 

 abandon the Saxon tongue and speak of the 

 vis medicatrix natures, the healing power of 

 nature. 



Now, all this is important in studying the 

 safeguards of the body against disease, be- 



